On-board fuel vapor separation for multi-fuel vehicle

ABSTRACT

A fuel delivery system for a fuel burning engine of a vehicle and a method of operating the fuel delivery system is provided. As one example, the method includes separating a first fuel and a second fuel from a fuel vapor on-board the vehicle, said fuel vapor including at least an alcohol component and a hydrocarbon component and said first fuel including a higher concentration of the alcohol component than the fuel vapor and the second fuel; condensing the separated first fuel from a vapor phase to a liquid phase; delivering the condensed liquid phase of the first fuel to the engine; and combusting at least the condensed liquid phase of the first fuel at the engine.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 13/398,754 filed Feb. 16, 2012, which is a divisional of U.S. patentapplication Ser. No. 11/955,246 filed Dec. 12, 2007, now U.S. Pat. No.8,118,009, the entire contents of each of which are incorporated hereinby reference for all purposes.

BACKGROUND AND SUMMARY

Internal combustion engines utilizing two or more different fuels havebeen proposed. As one example, the papers titled “Calculations of KnockSuppression in Highly Turbocharged Gasoline/Ethanol Engines Using DirectEthanol Injection” and “Direct Injection Ethanol Boosted GasolineEngine: Biofuel Leveraging for Cost Effective Reduction of OilDependence and CO2 Emissions” by Heywood et al. describe engines thatare capable of using multiple fuels. Specifically, the Heywood et al.papers describe directly injecting ethanol into the engine cylinders toimprove charge cooling effects, while relying on port injected gasolineto providing a majority of the combusted fuel over a drive cycle. Theethanol, in this example, can provide increased octane and increasedcharge cooling due to its higher heat of vaporization in comparison togasoline, thereby reducing knock limits on boosting and/or compressionratio. This approach purports to improve fuel economy and increaseutilization of renewable fuels.

The inventors of the present disclosure have recognized that requiring auser to re-fuel the engine system with two or more separate fuels (e.g.,gasoline and ethanol), in order to achieve the advantages described byHeywood et al., can be burdensome. To address this issue, the inventorsherein have provided a method of operating a fuel delivery system for afuel burning engine of a vehicle. The method can include: separating afirst fuel and a second fuel from a fuel vapor on-board the vehicle,said fuel vapor including at least an alcohol component and ahydrocarbon component and said first fuel including a higherconcentration of the alcohol component than the fuel vapor and thesecond fuel; condensing the separated first fuel from a vapor phase to aliquid phase; delivering the condensed liquid phase of the first fuel tothe engine; and combusting at least the condensed liquid phase of thefirst fuel at the engine.

By separating a fuel vapor into alcohol rich and hydrocarbon richcomponents, the benefits of increased engine performance and/or fueleconomy can be realized without requiring the vehicle operator to refuelthe vehicle with two or more separate fuels. Note that these fuel vaporsmay be generated on-board the vehicle from an initial liquid fuelmixture through the application of heat and/or vacuum. Additionally,fuel vapors may be generated from the fuel mixture during a refuelingoperation or during diurnal heating or cooling of the fuel system, evenwhen the vehicle is not in use.

The inventors have further recognized that in one approach, separationof a fuel vapor can be achieved by passing the fuel vapor through anadsorption device that adsorbs a hydrocarbon component of the fuel vaporat a higher rate than an alcohol component. However, in other examples,separation of the fuel vapor can be achieved by passing the alcoholcomponent of the fuel vapor through a selectively permeable membranethat transports the alcohol component of the fuel vapor at a higher ratethan the hydrocarbon component.

Further still, the inventors have recognized that these fuel vapors maybe separated using a batch processing approach, which can enable a morecontinuous fuel vapor separation operation where two or adsorptiondevices are utilized. As one example, the inventors have provided anengine system for a vehicle that includes: an internal combustion engineincluding an air intake passage; a fuel storage tank; an evaporatorconfigured to receive a fuel mixture from the fuel storage tank via afuel passage and to vaporize a higher volatility fuel from a lowervolatility fuel contained in the fuel mixture; a vapor separation systemincluding at least a first adsorption canister and a second adsorptioncanister arranged in parallel; a vapor passage fluidly coupling a vaporformation region of the evaporator with an inlet of each of the firstand second adsorption canisters of the separation system; a fuel vaporpurging passage fluidly coupling the air intake passage of the enginewith an outlet of each of the first and second adsorption canisters; anda control system configured to: operate the evaporator to vaporize thehigher volatility fuel from the lower volatility fuel; and during afirst mode, pass the higher volatility fuel through the first canisterto adsorb a hydrocarbon fraction of the higher volatility fuel at thefirst canister while purging fuel vapors from the second canister to theair intake passage of the engine; and during a second mode, pass thehigher volatility fuel through the second canister to adsorb thehydrocarbon fraction of the fuel vapor at the second canister whilepurging fuel vapors including the hydrocarbon fraction adsorbed duringthe first mode from the first canister to the air intake passage of theengine.

By periodically operating at least one of the adsorption devices toretain hydrocarbons of the fuel vapor while purging at least one otheradsorption device of previously stored hydrocarbons, a more continuousvapor separation process can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic depiction of an example fuel delivery processfor an internal combustion engine.

FIG. 2 shows a schematic diagram of an example of the fuel deliverysystem.

FIGS. 3 and 4 show flow charts depicting example control strategies foroperating a fuel delivery system.

FIGS. 5 and 6 show an example engine system in greater detail.

FIG. 7 shows a flow chart depicting an example control strategy foradjusting a relative amount of an alcohol rich fuel and a hydrocarbonrich fuel that are delivered to the engine.

FIG. 8 shows a fuel control map for selecting the ratio of ethanol andgasoline that are provided to the engine.

FIG. 9 shows a schematic depiction of an example separation deviceincluding a fuel separation membrane that selectively passes an alcoholcomponent of the fuel at a higher rate than a hydrocarbon component.

DETAILED DESCRIPTION

FIG. 1 shows a schematic depiction of a fuel delivery process 100 for aninternal combustion engine 120. As one example, engine 120 can beincluded in a vehicle propulsion system, which may further include atransmission. Note that the particular hardware enabling process 100will be described in greater detail with reference to FIGS. 2-4.

Fuel delivery process 100 can provide for the separation of an alcoholfuel component from an initial fuel mixture on-board the vehicle. As oneexample, a portion of the initial fuel mixture having a highervolatility (e.g. higher vapor pressure) can be evaporated or vaporizedby the application of heat to the fuel mixture and/or a partial vacuumat the vapor formation region or free surface of the liquid fuelmixture. An alcohol component of the more volatile vaporized portion ofthe fuel mixture can be separated from a hydrocarbon component by way ofselective adsorption of the hydrocarbon component onto a solid or by wayof a selective membrane that permits a greater transfer of the alcoholcomponent than the hydrocarbon component of the fuel vapor. In this way,an alcohol rich fuel can be separated from the fuel mixture, where itcan be provided to the engine in varying amounts relative to theremaining hydrocarbon rich fuel.

Fuel delivery process 100 can be performed with a fuel mixture 110residing initially in a liquid phase at a fuel storage tank on-board thevehicle. As one example, fuel mixture 110 can include a mixture of ahydrocarbon fuel including gasoline or diesel and an alcohol fuelincluding ethanol and/or methanol.

Note that hydrocarbon based fuels such as gasoline and diesel mayinclude various components. For example, gasoline may include a mixtureof hydrocarbons, aromatics, olefins, cyclo-alkanes, and heteroatomicorganic molecules. For purposes of clarity, when the term hydrocarboncomponent is used herein to distinguish a hydrocarbon based fuel such asgasoline or diesel from an alcohol based fuel such as ethanol ormethanol, it should be appreciated that the hydrocarbon component can beaccompanied by the aromatics, olefins, cyclo-alkanes, and/orheteroatomic organic molecules. As such, the various components thataccompany the hydrocarbon component of the hydrocarbon based fuelportion of the fuel mixture can be described for purposes of clarity assimply hydrocarbons or the hydrocarbon component.

As indicated at 170, a liquid phase of the fuel mixture can be providedto an evaporation or vaporization stage as indicated at 130 to separatea higher volatility vapor fraction 172 (e.g. having a higher vaporpressure) from a lower volatility liquid fraction (e.g. having a lowervapor pressure) indicated at 174 or 176. The lower volatility liquidfraction that is separated from the higher volatility vapor fraction canhave a higher octane rating than the original fuel mixture, where thelighter ends of the hydrocarbon component of the fuel mixture comprisesat least a portion of the separated higher volatility vapor fraction.

Separation of the fuel mixture initially received via 170 may includeheating the fuel mixture to separate the higher volatility fractionincluding at least alcohol and/or hydrocarbon component having a lowerboiling temperature (e.g. higher vapor pressure) and/or higherevaporation rate from the lower volatility fraction includinghydrocarbons having a higher boiling temperature (e.g. lower vaporpressure) and/or lower evaporation rate. For example, in addition to thealcohol vapors that are separated from the fuel mixture by evaporationor vaporization, the more volatile portion of gasoline may provide amixture of vapors including butane, pentane, hexanes, and the aromaticssuch as benzene, toluene, and xylenes.

Therefore, it should be appreciated that the more volatile fraction offuel mixture indicated at 172 may include some hydrocarbon vapors inaddition to alcohol vapors. Furthermore, in some examples, a partialvacuum may be applied at the vapor formation region of the fuel mixtureat 130 in order to increase the rate of evaporation of the more volatilefraction from the fuel mixture. The partial vacuum can be provided by apassage communicating with an air intake passage of the engine at areduced area region of the intake passage or downstream of an intakethrottle.

At 140, the more volatile fraction of the fuel mixture indicated at 172can undergo additional separation as indicated at 140. As one example, ahydrocarbon component of the more volatile fuel fraction received via172 can be separated from an alcohol component of the vapors asindicated at 178 and/or 180, in order to obtain an alcohol rich fuelcomponent as indicated at 177. As one non-limiting example, separationof the alcohol component from the hydrocarbon component at 140 can beachieved by adsorbing the hydrocarbon component at a solid containedwithin an adsorption canister while permitting the alcohol component topass through the canister without being adsorbed. As anothernon-limiting example, a selectively permeable membrane can be subjectedto the more volatile fuel vapor fraction, whereby the membrane permitsan exclusive or more rapid transport of the alcohol component throughthe membrane than the hydrocarbon component. Additionally, evaporativevapors indicated at 122 that originate from the initial fuel mixture 110can also undergo separation without necessarily passing through theevaporation or vaporization process indicated at 130.

As described herein, an alcohol rich fuel component is a relative termthat can refer to a first component of the fuel mixture that has agreater concentration of alcohol than a second component of the fuelmixture. Note that the term alcohol rich does not necessarily refer to afuel that includes pure alcohol, but may also include some hydrocarboncomponents. Similarly, a hydrocarbon rich fuel component is anotherrelative term that can refer to the second component of the fuel mixturethat has a higher concentration of hydrocarbons than the first alcoholrich component. The term hydrocarbon rich also does not necessarilyrefer to a fuel that includes pure hydrocarbons, but may also includessome alcohol components.

The hydrocarbon rich component of the more volatile fraction of the fuelmixture can be provided to the engine in a vapor phase as indicated at180 or can be condensed at 160 to obtain a liquid phase as indicated at182 or 184. The hydrocarbon rich component that is condensed at 160, canbe provided to the engine in liquid phase as indicated at 184.Alternatively, the liquid phase of the hydrocarbon rich component can bereturned to fuel mixture 110 as indicated at 182.

The alcohol rich component of the more volatile fraction of the fuelmixture can be condensed at 150 into a liquid phase as indicated at 179,wherein it may be provided to engine 120. In each of condensationprocesses indicated at 150 and 160, the fuel vapor can be condensed to aliquid phase by increasing the temperature and/or pressure of the vapor.Additionally, fuel mixture 110 can be provided directly to the engine ina liquid phase as indicated at 186.

In this way, engine 120 can receive a plurality of different substanceshaving different compositions and/or phases. However, in some examples,one or more of these substances may be omitted. For example, one or moreof the substances indicated at 179, 180, 184, 176, and/or 186 can beomitted from the fuel delivery process. In at least one example, thealcohol rich component in liquid phase (e.g. 179), the hydrocarbon richcomponent in vapor phase (e.g. 180), and the hydrocarbon rich componentin liquid phase (e.g. 184, 176, or 186) can be provided to the engine invarying relative amounts in response to operating conditions.

In some examples, where two or more different substances havingdifferent concentrations of alcohol are provided to the engine, separatefuel injectors may be used to independently deliver the fuels to thevarious cylinders of the engine. As one example, a first fuel injectorcan be used to provide an alcohol rich liquid fuel to a first locationof the engine and a second fuel injector can be used to provide ahydrocarbon rich liquid fuel to a second location of the engine. Forexample, a first injector can be configured as a port injector fordelivering a hydrocarbon rich fuel while a second injector can beconfigured as a direct injector for delivering an alcohol rich fuel.However, in some examples, a plurality of different liquid fuels can beprovided to the engine via a common fuel injector by way of anintermediate mixing valve. Furthermore, fuel vapors (e.g. as indicatedat 180) can be provided to the engine via a fuel vapor vent valvecommunicating with an air intake passage of the engine as will bedescribed with reference to FIG. 6. Regardless of the particular mannerin which these various fuels are provided to the engine, engine 120 canreceive intake air from ambient as indicated at 188 which can be mixedwith the fuel. This air and fuel mixture can be combusted in the variousengine cylinders to produce a mechanical output and resulting exhaustgases indicated at 290.

FIG. 2 shows an example fuel delivery system 200 including examplehardware for implementing the fuel delivery process of FIG. 1. Fuelsystem 200 may include a fuel storage tank 210 which can be configuredto store the liquid fuel mixture 110. Fuel storage tank 210 can includea fuel sensor 216 for providing to control system 290, an indication ofthe amount of fuel contained in fuel storage tank 210. Fuel storage tank210 can also include a fuel sensor 218 for providing to control system290, an indication of fuel composition.

In this particular example, fuel storage tank 210 can communicate withengine 120 via a plurality of fuel paths as previously described withreference to FIG. 1. For example, evaporative vapor 112 from the liquidfuel mixture stored in fuel storage tank 210 can proceed via fuel vaporpassage 212 to a vapor separation system indicated at 240 where ahydrocarbon component can be removed from the fuel vapor by passing theevaporative vapors through one or more canisters 242 and 244, enablingthe alcohol component to pass through vapor separation system 240. Thehydrocarbon component can be removed from the fuel vapor by thecanisters via adsorption of the hydrocarbons contained in the vapor ontoa adsorption solid or other suitable material residing within thecanisters. As one non-limiting example, to selectively strip gasolinecomponents from the alcohols contained in the vapor, the vapors can bepassed through the canisters including a bed of TENAX, carbon, or othersuitable material, which has a low affinity for alcohols, but a highaffinity for hydrocarbons and aromatics. The canisters can beperiodically purged of their adsorbed components by exposing thecanisters to a cooler gas, such as ambient air, which can cause thecanisters to desorb the gasoline components. An alternative embodimentof vapor separation system 240 is shown in FIG. 9, which instead relieson a selectively permeable fuel separation membrane rather thanadsorption onto a sold.

Fuel vapor passage 212 can include a unidirectional check valve shownschematically at 214 to reduce or inhibit the flow of fuel back into thefuel storage tank from passage 272. Fuel vapor passage 212 can befluidly coupled with a fuel vapor formation region of the fuel storagetank, which may reside near an upper region (relative to thegravitational vector) of the storage volume defined by the fuel tank. Inthis way, fuel vapors originating from the fuel mixture during are-fueling operation or during diurnal heating and cooling of the fuelmixture can be transferred to separation system 240, which is alsoconfigured to receive fuel vapors from evaporator 230.

The fuel mixture in a liquid state can be provided to fuel evaporator230 via a fuel passage 270, whereby evaporation or vaporization of themore volatile fraction of the fuel mixture may be performed, aspreviously described with reference to 130, by application of heatand/or a vacuum. Fuel passage 270 can include a check valve 271 toreduce or inhibit the flow of fuel back into the fuel storage tank fromevaporator 230. Evaporator 230 can communicate thermally with a heatsource such as the engine coolant, exhaust system of the engine, or anelectric heater, which is shown schematically at 232. Heat transferredfrom the heat source to the evaporator can be used to heat the fuelmixture to a suitable temperature to facilitate vaporization orevaporation of the more volatile fraction of the fuel mixture, includingat least the alcohol component.

The temperature of the evaporator can be controlled by varying anoperating parameter of the heat source (e.g. temperature or thermalenergy power output) and/or the rate of heat transfer between the heatsource and the fuel mixture in order to maintain the fuel mixture at atemperature that is less than a temperature where the heavierhydrocarbons contained in the fuel mixture are readily vaporized. As oneexample, the rate of heat exchange between the heat source and the fuelmixture can be adjusted by varying the flow rate of a working fluidprovided to evaporator 230 via passage 232. For example, a thermostatindicated generally at 213 can provide an indication of fuel mixturetemperature to a valve 215 for controlling the flow rate of the workingfluid within circuit 232.

The liquid portion of the fuel mixture including the less volatilehydrocarbon fraction of the fuel (e.g. indicated as 174 in FIG. 1) canbe returned to the fuel storage tank via fuel passage 274. Fuel passage274 can include a valve 234, which may be adjusted by the control systemto regulate the flow of fuel returning to the fuel storage tank. In someexamples, fuel passage 274 may include a heat exchanger for reducing thetemperature of the liquid fuel before it is returned to the fuel tank.In this way, additional increase in fuel temperature at the fuel tankcan be reduced in the case where fuel is returned to the tank.Furthermore, in some examples, the less volatile portion of the fuelmixture, including at least the heavier hydrocarbons (e.g. indicated at176 in FIG. 1) can be provided to the engine via a fuel passage 276.

The more volatile vapor portion of the fuel mixture including at leastthe alcohol component and potentially some lighter hydrocarbons (e.g.indicated at 172 in FIG. 1) can be provided to separation system 240 viaa fuel vapor passage 272, which is fluidly coupled with a vaporformation region of evaporator 230. As depicted schematically in FIG. 2,fuel passages 274 and/or 276 can communicate with a lower region of thefuel evaporator (e.g. via a drain) and fuel vapor passage 272 cancommunicate with an upper region of the fuel evaporator, therebyimproving the separation of the heavier liquid phase of the fuel mixturefrom the lighter vapor phase of the fuel mixture. Additionally, a vacuumcan be applied at the evaporator via vapor passage 272 from intakemanifold 226 to further assist in the removal of more volatile fuelvapors from evaporator 230. As one example, an intake throttle of theengine can be adjusted to vary the pressure within the intake passage ofthe engine, thereby varying the vacuum applied to the evaporator viapassage 272.

The vapor phase of the fuel mixture generated at evaporator 230 can beprovided to separation system 240 via one or more vapor passagescommunicating with passage 272. In this particular example, separationsystem 240 includes two adsorption canisters 242 and 244 that cancommunicate with fuel vapor passage 272 via passages 236 and 235,respectively. Air may be received from ambient as indicated at 188 andcan be provided to passage 236 via air passage 238 and to passage 235via air passage 237 for purging the canisters of stored hydrocarbons. Avalve indicated at 233 can be adjusted by control system 290 to enablecanister 242 to receive intake air via passage 238 or instead receivefuel vapors from the evaporator via passage 236. Similarly, a valveindicated at 231 can be adjusted by control system 290 to enablecanister 244 to receive intake air via passage 237 or fuel vapor viapassage 235. Valves 233 and 231 can include three-way valves or othersuitable valves for enabling control system 290 to select which one oftwo flow paths are communicating with the adsorption canisters.

Depending on the positions of valves 243 and 241, canisters 242 and 244can respectively communicate with condenser 250 via vapor passages 246and 245, and can respectively communicate with purge passage 280 viavapor passages 248 and 247. As one non-limiting example, the controlsystem can coordinate the adjustment of valves 231, 233, 241, and 243 toutilize a first canister of separation system 240 to remove the alcoholvapor component from the hydrocarbon vapor component, while a secondcanister of the separation system can be purged of the hydrocarboncomponent that has been stored at the second canister by adsorption.

Referring also to FIG. 3, a flow chart depicting an example controlstrategy for operating separation system 240 will be described. If at310, hydrocarbons are to be purged from canister 242, then the routinemay proceed to 312. Otherwise, the routine can proceed to 318. Forexample, at 310, the control system may judge whether to purgehydrocarbons stored in canister 242. The control system may purgecanister 242 in response to an indication of the amount of hydrocarbonscontained in the canister relative to the hydrocarbon storage capacityof the canister. These indications may include: a period of time since aprevious purge of the canister, an amount of alcohol that has passedthrough the canister since a previous purge, a temperature of thecanister, a mass of the canister, and/or a pressure difference acrossthe canister, etc.

For example, canisters 242 and 244 may include temperature sensorsarranged upstream, downstream, or at the canister, and in communicationwith control system 290 to provide an indication of temperature. Asanother example, pressure sensors may be provided upstream anddownstream of the canisters, which can communicate with control system290 to provide an indication of pressure drop through the canisters.

Canister 242 may be purged of hydrocarbons by performing operations312-314. At 312, valve 233 can be adjusted to open air passage 238 tocanister 242 and close vapor passage 236. At 314, valve 243 may beadjusted to close vapor passage 246 and open passage 248 to canister242. At 316, purge valve 282 can be adjusted to vary the flow rate ofhydrocarbon vapors that are purged to the engine. In this way, thecontrol system can operate separation system 140 so that canister 242 ispurged of hydrocarbons by enabling air to flow from the ambient to thelower pressure of intake manifold 226 via canister 242, thereby carryingwith it the stored hydrocarbon vapors.

If at 318, hydrocarbons are to be stored at canister 242, then theroutine can proceed to 320. Otherwise, the routine can proceed to 324.For example, at 318, the control system may judge whether to storehydrocarbons at canister 242. As one example, the control system maystore hydrocarbons at canister 242 if evaporator 230 is generating fuelvapors and/or canister 244 is nearing its hydrocarbon storage capacityor is conducting a purge. At 320, valve 233 can be adjusted to openvapor passage 236 to canister 242 and close air passage 238. At 322,valve 243 may be adjusted to open vapor passage 246 to canister 242 andclose passage 248, thereby directing fuel vapors produced by theevaporator through canister 242 where the hydrocarbon component of thefuel vapors may be trapped and the alcohol component can proceed tocondenser 250.

If at 324, hydrocarbons are to be purged from canister 244, then theroutine may proceed to 326. Otherwise, the routine can proceed to 332.For example, at 324, the control system may judge whether to purgehydrocarbons stored in canister 244. The control system may purgecanister 244 in response to an indication of the amount of hydrocarbonscontained in the canister relative to the hydrocarbon storage capacityof the canister. As previously described with reference to canister 242,these indications may include: a duration of time since a previous purgeof the canister, an amount of alcohol condensed from the fuel vaporpassing through the canister, a temperature of the canister, a mass ofthe canister, and/or a pressure difference across the canister, etc.

Canister 244 may be purged of hydrocarbons by performing operations326-330. At 326, valve 231 can be adjusted to open air passage 237 tocanister 244 and close vapor passage 235. At 328, valve 241 may beadjusted to close vapor passage 245 and open passage 247 to canister244. At 330, purge valve 282 can be adjusted to vary the flow rate ofhydrocarbon vapors that are purged to the engine. In this way, thecontrol system can operate separation system 140 so that canister 244 ispurged of hydrocarbons by enabling air to flow from ambient to the lowerpressure intake manifold of the engine via canister 244, therebycarrying with it the stored hydrocarbon vapors. If at 332, hydrocarbonsare to be stored at canister 244, then the routine can proceed to 334.Otherwise, the routine can return. For example, at 332, the controlsystem can judge whether to store hydrocarbons at canister 244. As oneexample, the control system may store hydrocarbons at canister 244 ifevaporator 230 is generating fuel vapors and/or canister 242 is nearingits hydrocarbon storage capacity or is conducting a purge. At 334, valve231 can be adjusted to open vapor passage 235 to canister 244 and closeair passage 237. At 336, valve 241 may be adjusted to open vapor passage245 to canister 244 and close passage 247, thereby directing fuel vaporsproduced by the evaporator through canister 244 where the hydrocarboncomponent of the fuel vapors may be trapped and the alcohol componentcan proceed to condenser 250.

While FIG. 3 describes how canisters 242 and 244 can be operated tostore or purge hydrocarbons, FIG. 4 describes how canisters 242 and 244can be coordinated to enable batch processing of the fuel vapor mixtureproduced by the evaporator. At 410, if the amount of hydrocarbon fuelstored at the first canister is exceeding a storage threshold of thefirst canister, then the routine may proceed to 420. Otherwise, theroutine may return where the first canister can continue to store thehydrocarbon fraction of the fuel mixture vapor while passing the alcoholcomponent to the condenser. At 420, the second canister may be switchedfrom the purging operation to the storage operation and the firstcanister can be purged of the stored hydrocarbons.

Continuing with FIG. 4, at 430, if it is judged that the amount ofhydrocarbons stored at the second canister is exceeding a storagethreshold of the second canister, then the routine may proceed to 440.Otherwise, the routine may return, where the second canister cancontinue to store the hydrocarbon component of the fuel mixture vaporwhile passing the alcohol component to the condenser. At 440, the firstcanister may be switched from the purging operation to the storageoperation and the second canister may be purged of the storedhydrocarbons. In this way, evaporative fuel vapors produced by theevaporator and/or fuel storage tank can be passed through one of atleast two adsorption canisters to remove hydrocarbons while the othercanister is purging a batch of previously stored hydrocarbons to theengine. Note that in some examples, separation system 240 may includeonly a single adsorption canister.

Alcohol vapors (e.g. indicated as 177 in FIG. 1) that pass throughseparation system 240 via one or more canisters (or other suitableseparation system) can be provided to condenser 250 by way of vaporpassage 277 communicating with passages 245 and 246. Condenser 250 canbe configured to condense alcohol vapor received from the separationsystem to a liquid state indicated at 179. The alcohol in the liquidstate can be provided to the engine via a fuel passage 279. As oneexample, condenser 250 can be configured to increase the pressure and/ortemperature applied to the alcohol vapor in order to promotecondensation. Condenser 250 can receive a working fluid via coolingcircuit 252 having a lower temperature than the alcohol vapor receivedfrom the separation system. For example, the working fluid may includeambient air or a refrigerant utilized by the on-board air conditioningunit. As yet another example, a thermoelectric cooling device may beutilized to cool the alcohol vapor at the condenser. A thermostat 253can provide an indication of the temperature of the alcohol withincondenser 250 to a valve 255 that regulates the flow of the workingfluid through cooling circuit 252. As depicted schematically in FIG. 2,vapor passage 277 can communicate with an upper region of condenser 250and fuel passage 279 for receiving the liquid alcohol can communicatewith a lower region of condenser 250 (e.g. a drain) to promoteseparation of the vapor and liquid phases of the alcohol.

FIG. 2 provides an approach whereby a fuel mixture can be separated intoa first fuel (an alcohol rich fuel) having a higher concentration ofalcohol and a lower concentration of hydrocarbons than a second fuel (ahydrocarbon rich fuel). The first fuel including at least liquid alcohol(e.g. indicated as 179 in FIG. 1) can be provided to each of the enginecylinders via a first fuel injection system indicated generally at 222.The second fuel including at least the liquid hydrocarbons (e.g.indicated as 176, 184, or 186 in FIG. 1) can be provided to the each ofthe engine cylinders via a second fuel injection system indicatedgenerally at 224.

As one non-limiting example, fuel injection system 222 for the alcoholrich fuel may include an injector for each cylinder that is separatefrom an injector of fuel injection system 224 for the second fuel, asshown in FIG. 6. However, in other examples, the alcohol rich fuel andthe hydrocarbon rich fuel can be combined at a single injector by way ofa mixing valve to enable a mixture of the alcohol rich fuel and thehydrocarbon rich fuel to be provided to the engine in varying ratios.Regardless of how the alcohol rich fuel and the hydrocarbon rich fuelare provided to the engine, these fuels can be combusted to generatemechanical work and products of the combustion can be exhaust from theengine via exhaust passage 228.

Fuel delivery system 200 can include various fuel buffers to maintain asuitable supply of alcohol rich fuel and/or hydrocarbon rich fuel foruse by the engine even during transient conditions. For example, astorage tank 206 may be provided along fuel passage 279 downstream ofcondenser 250 to store the alcohol rich fuel. Storage tank 206 mayinclude a sensor 205 for providing an indication to control system 290of the amount of alcohol rich fuel stored in tank 206. Tank 206 may alsoinclude a sensor 207 for providing an indication of the composition ofthe fuel stored in tank 206, including an indication of theconcentration of alcohol in the alcohol rich fuel. In some examples, astorage tank 208 may be provided for the hydrocarbon rich fuel. Tank 208can also include a sensor 209 for providing an indication of the amountof hydrocarbon rich fuel stored in tank 208 and/or a sensor 203 forproviding an indication of the composition of the fuel stored in tank208. In this way, the control system can identify the amount and/orcomposition of the alcohol rich fuel and the hydrocarbon rich fuel thatare available to the engine. However, in some examples, storage tanks206 and/or 208 may be omitted.

In response to an indication of a low availability of the alcohol richfuel (e.g. when tank 206 is approaching an empty condition), forexample, as provided by sensor 205, the control system can increase therate of evaporation at evaporator 230, separation at separator 240,and/or condensation at condenser 250 to increase the separation rate ofthe alcohol fuel component from the hydrocarbon fuel component.Similarly, in response to an indication of a greater availability of thealcohol rich fuel (e.g. when tank 206 is approaching a full condition),the rate of evaporation, separation, and/or condensation may be reduced.The rate of fuel vapor generation can be increased by increasing theflow rate of the mixed fuel to the evaporator and/or by increasing theamount of heat provided to the evaporator via heating circuit 232. Therate of fuel vapor generation can be reduced by reducing the flow rateof the mixed fuel to the evaporator and/or by reducing the amount ofheat provided to the evaporator via heating circuit 232. Similarly, therate of condensation of the alcohol fraction can be increased ordecreased by adjusting the flow rate of coolant flowing throughcondenser 250 via cooling circuit 252.

As yet another example, the control system can monitor the usage rate ofeach fuel type (e.g. via changes in fuel storage amount and/or fuelinjector pulse width and injection frequency) and can adjust theprocessing rate (e.g. evaporation, separation, and condensation) of thefuel mixture accordingly to ensure that a sufficient amount of each fuelcomponent is available to the engine.

As still another example, when the control system identifies that thefuel contained in fuel tank 210 includes an insufficient concentrationof alcohol, for purposes of separating the fuel components, the controlsystem may reduce or discontinue the various operations at evaporator230, vapor separator 240, and/or condenser 250. For example, where thefuel contained in fuel tank 210 includes pure gasoline, the controlsystem may shut-off evaporator 230 and condenser 250 to conserve energy.In this case, the fuel can be provided directly to the engine by way ofpassages 201 and 276, thereby bypassing the evaporator, separator,and/or condenser.

The control system can also effectuate increases or decreases in fuelflow rate, the flow rate of the working fluid flowing through circuit232, and the flow rate of the working fluid flowing through circuit 252by adjusting the operation of intermediate valves and/or pumps not shownin FIG. 2. For example, fuel passage 270 may include a fuel pump that iscontrollable by control system 290. As another example, fuel passages276 and 279 can include fuel pumps for providing sufficient fuelpressure to the fuel injection systems. By increasing the pump workand/or pressure increase, the flow rate of fuel to the evaporator can beincreased. By opening valve 232 or increasing the pump work provided toheating circuit 232, the flow rate of the working fluid may beincreased. In this way, the control system can adjust various parametersof the fuel delivery system to meet the particular fuel consumption rateof the engine. Additionally, as depicted schematically at 201, a fuelbypass may be provided to couple fuel storage tank 210 with fuel passage276 and/or hydrocarbon rich storage tank 208. Thus, under conditionswhere the evaporator is to be bypassed to at least some extent, the fuelmixture contained in tank 210 can be provided directly to the enginewithout requiring that it first pass through the evaporator. In responseto the decision to bypass the evaporator and supplement the hydrocarbonrich fuel with the fuel mixture, the control system can reduce theamount of alcohol rich fuel delivered to the engine to account foralcohol already contained in the fuel mixture. Thus, a fuel compositionsensor at fuel storage tank 210 or 208 can provide an indication to thecontrol system of concentration of alcohol contained in the fuelinjected by fuel injection system 224 and make appropriate adjustment tothe amount of alcohol rich fuel delivered to the engine via fuelinjection system 222. Fuel injection system 222 and 224 will bedescribed in greater detail with reference to FIG. 6, whereby fuelinjector 666A can receive fuel from fuel injection system 222 and fuelinjector 666B can receive fuel from fuel injection system 224.

FIGS. 5 and 6 provide a schematic depiction of engine 120 in greaterdetail. FIG. 6 shows an example cylinder of a multi-cylinder engine 120,as well as the intake and exhaust path connected to that cylinder. Inthe example embodiment shown in FIG. 6, engine 120 is capable of usingtwo different fuels (e.g. an alcohol rich fuel and a hydrocarbon richfuel) via two different injectors. For example, engine 120 mayselectively utilize a hydrocarbon rich fuel including gasoline and analcohol rich fuel including ethanol and/or methanol. In otherembodiments, a single injector (such as a direct injector) may be usedto inject a mixture of gasoline and an alcohol fuel, where the ratio ofthe two fuel quantities in the mixture may be adjusted by controller 290via a mixing valve, for example.

Gasoline (or other hydrocarbon) and alcohol can be selectively used invarying relative amounts to take advantage of the increased chargecooling provided by the alcohol fuel (e.g., via direct injection) tothereby reduce the tendency of engine knock. This phenomenon, combinedwith increased compression ratio, boosting and/or engine downsizing, canthen be used to obtain substantial fuel economy benefits by reducing theknock limitations on the engine.

FIG. 6 shows one example fuel injection system with two fuel injectorsper cylinder, for at least one cylinder. However, each cylinder of theengine may also include two fuel injectors. The two injectors may beconfigured in various locations, such as two port injectors, one portinjector and one direct injector (as shown in FIG. 6), or two directinjectors. Combustion chamber 630 of engine 120 is shown includingcombustion chamber walls 632 with piston 636 positioned therein andconnected to crankshaft 640. A starter motor (not shown) may be coupledto crankshaft 640 via a flywheel (not shown), or alternatively directengine starting may be used.

Combustion chamber, or cylinder, 630 is shown communicating with intakemanifold 544 and exhaust manifold 548 via respective intake valves 652 aand 652 b (not shown), and exhaust valves 654 a and 654 b (not shown).Thus, while four valves per cylinder may be used, in another example, asingle intake and single exhaust valve per cylinder may also be used. Instill another example, two intake valves and one exhaust valve percylinder may be used.

Combustion chamber 630 can have a compression ratio, which may bedefined as the ratio of the volume of the combustion chamber when piston636 is at bottom center to the volume of the combustion chamber when thepiston is at top center. In one example, the compression ratio may beapproximately 9:1, between 10:1 and 11:1, or between 11:1 and 12:1, oreven greater.

Fuel injector 666A is shown directly coupled to combustion chamber 630for delivering injected fuel directly therein in proportion to the pulsewidth of signal dfpw received from controller 290 via electronic driver668A. While FIG. 6 shows injector 666A positioned at a side wall ofcylinder, it may also be located overhead of the piston, such as nearthe position of spark plug 592. Such a position may improve mixing andcombustion due to the lower volatility of some alcohol based fuels.Alternatively, the injector may be located overhead and near the intakevalve to improve mixing.

The alcohol rich fuel may be delivered to fuel injector 666A by a highpressure fuel injection system 222 shown schematically in FIG. 2, alsoincluding a fuel tank, a fuel pump or pumps, and a fuel rail. As anotherexample, the alcohol rich fuel may be delivered by a single stage fuelpump at lower pressure, in which case the timing of the direct fuelinjection may be more limited during the compression stroke than if ahigh pressure fuel system were instead used.

Fuel injector 666B is shown coupled to intake manifold 444 in thisexample, rather than directly to cylinder 630. Fuel injector 666B candeliver the hydrocarbon rich fuel in proportion to the pulse width ofsignal pfpw received from controller 290 via electronic driver 668B asshown in FIG. 2 as fuel injection system 224. Note that a single driver668 may be used for both fuel injection systems, or multiple drivers maybe used. Fuel separation system 240 including one or more canisters forstoring hydrocarbon vapors are also shown in schematic formcommunicating with intake manifold 544. Various fuel systems and fuelvapor purge systems may be used, such as those described below hereinwith regards to FIGS. 1 and 2, for example.

Intake manifold 544 is shown communicating with throttle body 658 viathrottle plate 562. In this particular example, throttle plate 562 iscoupled to electric motor 694 so that the position of ellipticalthrottle plate 562 may be controlled by control system 290 via electricmotor 694. This configuration may be referred to as electronic throttlecontrol (ETC), which can also be utilized during idle speed control. Inan alternative embodiment (not shown), a bypass air passageway may bearranged in parallel with throttle plate 562 to control inducted airflowduring idle speed control via an idle control by-pass valve positionedwithin the air passageway.

Exhaust gas sensor 676 is shown coupled to exhaust manifold 548 upstreamof catalytic converter 570, where sensor 676 can correspond to variousexhaust sensors. For example, sensor 676 may be suitable sensor forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor, a UEGO, a two-state oxygen sensor, an EGO, a HEGO, or anHC or CO sensor. In this particular example, sensor 676 is a two-stateoxygen sensor that provides signal EGO to control system 290 whichconverts signal EGO into two-state signal EGOS. A high voltage state ofsignal EGOS indicates exhaust gases are rich of stoichiometry and a lowvoltage state of signal EGOS indicates exhaust gases are lean ofstoichiometry. Signal EGOS may be used to advantage during feedbackair/fuel control to maintain average air/fuel at stoichiometry during astoichiometric homogeneous mode of operation.

Distributorless ignition system 588 selectively provides ignition sparksto combustion chamber 630 via spark plug 592 in response to sparkadvance signal SA from control system 290. Control system 290 may causecombustion chamber 630 to operate in a variety of different combustionmodes, including a homogeneous air/fuel mode and a stratified air/fuelmode by controlling injection timing, injection amounts, spray patterns,etc. Further, combined stratified and homogenous mixtures may be formedin the chamber. In one example, stratified layers may be formed byoperating injector 666A during a compression stroke. In another example,a homogenous mixture may be formed by operating one or both of injectors666A and 666B during an intake stroke (which may be open valveinjection). In yet another example, a homogenous mixture may be formedby operating one or both of injectors 666A and 666B before an intakestroke (which may be closed valve injection). In still other examples,multiple injections from one or both of injectors 666A and 666B may beused during one or more strokes (e.g., intake, compression, exhaust,etc.). Even further examples may be where different injection timingsand mixture formations are used under different conditions, as describedbelow. Control system 290 can control the amount of fuel delivered byfuel injectors 666A and 666B so that the homogeneous, stratified, orcombined homogenous/stratified air/fuel mixture in chamber 630 can beselected to be at stoichiometry, a value rich of stoichiometry, or avalue lean of stoichiometry. Emission control device 672 is shownpositioned downstream of catalytic converter 570. Emission controldevice 672 may be a three-way catalyst or a NOx trap, or a combinationthereof.

Control system 290 is shown as a microcomputer, including microprocessorunit 602, input/output ports 604, an electronic storage medium forexecutable programs and calibration values shown as read only memorychip 606 in this particular example, random access memory 608, keepalive memory 610, and a conventional data bus. Control system 290 isshown receiving various signals from sensors coupled to engine 10, inaddition to those signals previously discussed, including measurement ofinducted mass air flow (MAF) from mass air flow sensor 500 coupled tothrottle body 658; engine coolant temperature (ECT) from temperaturesensor 512 coupled to cooling sleeve 514; a profile ignition pickupsignal (PIP) from Hall effect sensor 518 coupled to crankshaft 640; andthrottle position TP from throttle position sensor 520; absoluteManifold Pressure Signal MAP from sensor 522; an indication of knockfrom knock sensor 682; and an indication of absolute or relative ambienthumidity from sensor 680. Engine speed signal RPM is generated bycontrol system 290 from signal PIP in a conventional manner and manifoldpressure signal MAP from a manifold pressure sensor provides anindication of vacuum, or pressure, in the intake manifold. Duringstoichiometric operation, this sensor can give an indication of engineload. Further, this sensor, along with engine speed, can provide anestimate of charge (including air) inducted into the cylinder. In a oneexample, sensor 518, which is also used as an engine speed sensor,produces a predetermined number of equally spaced pulses everyrevolution of the crankshaft.

In this particular example, temperature Tcat1 of catalytic converter 570is provided by temperature sensor 524 and temperature Tcat2 of emissioncontrol device 672 is provided by temperature sensor 526. In analternate embodiment, temperature Tcat1 and temperature Tcat2 may beinferred from engine operation.

Continuing with FIG. 6, a variable camshaft timing system is shown.Specifically, camshaft 530 of engine 120 is shown communicating withrocker arms 532 and 534 for actuating intake valves 652 a, 652 b andexhaust valves 654 a, 654 b. Camshaft 530 is directly coupled to housing136. Housing 136 forms a toothed wheel having a plurality of teeth 138.Housing 136 is hydraulically coupled to crankshaft 40 via a timing chainor belt (not shown). Therefore, housing 536 and camshaft 530 rotate at aspeed that can be the same as or a multiple of the crankshaft speed.However, by manipulation of the hydraulic coupling as will be describedlater herein, the relative position of camshaft 530 to crankshaft 640can be varied by hydraulic pressures in advance chamber 642 and retardchamber 644. By allowing high pressure hydraulic fluid to enter advancechamber 642, the relative relationship between camshaft 530 andcrankshaft 640 is advanced. Thus, intake valves 652 a, 652 b and exhaustvalves 654 a, 654 b open and close at a time earlier than normalrelative to crankshaft 640. Similarly, by allowing high pressurehydraulic fluid to enter retard chamber 644, the relative relationshipbetween camshaft 530 and crankshaft 640 is retarded. Thus, intake valves652 a, 652 b, and exhaust valves 654 a, 654 b open and close at a timelater than normal relative to crankshaft 640.

While this example shows a system in which the intake and exhaust valvetiming are controlled concurrently, variable intake cam timing, variableexhaust cam timing, dual independent variable cam timing, or fixed camtiming may be used. Further, variable valve lift may also be used and/orcamshaft profile switching may be used to provide different cam profilesunder different operating conditions. Further still, the valvetrain maybe roller finger follower, direct acting mechanical bucket,electromechanical, electrohydraulic, or other alternatives to rockerarms.

Continuing with the variable cam timing system, teeth 538, being coupledto housing 536 and camshaft 530, allow for measurement of relative camposition via cam timing sensor 550 providing signal VCT to controlsystem 290. Teeth 501, 502, 503, and 504 are preferably used formeasurement of cam timing and are equally spaced (for example, in a V-8dual bank engine, spaced 90 degrees apart from one another) while tooth505 is preferably used for cylinder identification, as described laterherein. In addition, control system 290 can send control signals (LACT,RACT) to conventional solenoid valves (not shown) to control the flow ofhydraulic fluid either into advance chamber 642, retard chamber 644, orneither chamber.

Relative cam timing can be measured in a variety of ways. In generalterms, the time, or rotation angle, between the rising edge of the PIPsignal and receiving a signal from one of the plurality of teeth 538 onhousing 536 gives a measure of the relative cam timing. For theparticular example of a V-8 engine, with two cylinder banks and afive-toothed wheel, a measure of cam timing for a particular bank isreceived four times per revolution, with the extra signal used forcylinder identification.

Sensor 560 may also provide an indication of oxygen concentration in theexhaust gas via signal 562, which provides control system 290 a voltageindicative of the O2 concentration. For example, sensor 560 can be aHEGO, UEGO, EGO, or other type of exhaust gas sensor. Also note that, asdescribed above with regard to sensor 676 and sensor 560 can correspondto various different sensors.

FIG. 6 merely shows one cylinder of a multi-cylinder engine, and thateach cylinder has its own set of intake/exhaust valves, fuel injectors,spark plugs, etc. For example, referring also to FIG. 5, engine 120 isshown having four in-line cylinders, however, engine 120 may have anysuitable number of cylinders. Engine 120 may include a boosting deviceincluding a compression device such as turbocharger 519, which has aturbine 519 a coupled in the exhaust manifold 548 and a compressor 519 bcoupled in the intake manifold 544. While FIG. 5 does not show anintercooler, one may optionally be included. Turbine 519 a is typicallycoupled to compressor 519 b via a drive shaft 515. Various types ofturbochargers arrangements may be used. For example, a variable geometryturbocharger (VGT) may be used where the geometry of the turbine and/orcompressor may be varied during engine operation by control system 290to vary the boost pressure provided to engine 120. Alternately, or inaddition, a variable nozzle turbocharger (VNT) may be used when avariable area nozzle is placed upstream and/or downstream of the turbinein the exhaust line (and/or upstream or downstream of the compressor inthe intake line) for varying the effective expansion or compression ofgasses through the turbocharger. Still other approaches may be used forvarying expansion in the exhaust, such as a waste gate valve. FIG. 5shows an example bypass valve 520 around turbine 519 a and an examplebypass valve 522 around compressor 519 b, where each valve may becontroller via control system 290 to vary the boost pressure that isprovided to engine 120. In some examples, a twin turbochargerarrangement, and/or a sequential turbocharger arrangement, may be used.In the case of multiple adjustable turbocharger and/or stages, it may bedesirable to vary a relative amount of expansion though theturbocharger, depending on operating conditions (e.g. manifold pressure,airflow, engine speed, etc.). Further, a supercharger may be used instill other examples.

FIG. 7 shows a flow chart depicting an example method for controllingthe delivery of the alcohol rich fuel and the hydrocarbon rich fuel tothe engine. At 710, operating conditions of the engine and fuel systemmay be identified. For example, the control system can obtain operatingcondition information from various sensors previously described.Operating conditions may include: engine speed, engine load, enginetemperature, boost pressure, turbocharger conditions, ambientconditions, amount of separated and un-separated fuel stored on-boardthe vehicle, composition and amount of each fuel type available fordelivery to the engine, requested engine performance by the operator(e.g. via an input received from an accelerator pedal), usage rate ofeach fuel type, among other operating conditions.

At 720, the hydrocarbon rich fuel and the alcohol rich fuel can beprovided to the engine in varying relative amounts in response to theoperating conditions identified at 710. For example, the control systemcan vary the amount of an alcohol rich fuel such as ethanol relative tothe amount of a hydrocarbon rich fuel such as gasoline that are providedto the engine in response to operating conditions such as boost pressureprovided by a boosting device, engine load, and engine speed, etc. Thecontrol system can also utilize an indication of the composition of thealcohol rich fuel and hydrocarbon rich fuel when selecting the relativeamounts of each to be provided to the engine. For example, the controlsystem can reduce the amount of the alcohol rich fuel that is providedto the engine relative to the hydrocarbon rich fuel, when thehydrocarbon rich fuel also includes some alcohol. Furthermore, thecontrol system can adjust the amount of the alcohol rich fuel and thegasoline rich fuel that are provided to the engine so that a target airto fuel ratio is combusted in the engine cylinders.

As described with reference to FIG. 6, in at least some examples, thealcohol rich fuel can be provided directly to the engine cylinders viain-cylinder direct fuel injectors and the hydrocarbon rich fuel can beprovided to the engine cylinders via a separate set of port injectors oralternatively via separate direct injectors. In still other examples,the hydrocarbon rich fuel and the alcohol rich fuel can be provided toeach of the engine cylinders via a single in-cylinder direct injectorthat includes a mixing valve arranged upstream of the injector foradjusting the relative amounts of each fuel to be introduced by theinjector.

At 730, if the operating conditions provide an indication of engineknock, then the amount of alcohol rich fuel that is provided to theengine relative to the amount of the hydrocarbon rich fuel may beincreased at 740 to reduce or eliminate the engine knock. In someexamples, the engine may include a knock sensor that is communicativelycoupled with the control system for enabling the control system toresponse to an indication of engine knock by increasing the relativeamount of alcohol that is delivered to the engine. Finally, the routinemay return to the start.

FIG. 8 shows an example map that may be used by the control system forselecting the appropriate ratio of the alcohol rich fuel and thegasoline rich fuel in response to changing operating conditions. Forexample, as indicated at 810, the ratio of an alcohol rich fuel such asethanol may be increased relative to a hydrocarbon rich fuel includinggasoline in response to increasing engine load, engine speed, and engineboost, among other operating conditions that may affect engine knock. Asone example, FIG. 8 represents a map that may be stored in memory at thecontrol system.

FIG. 9 shows a schematic depiction of an alternative embodiment ofseparator 240 previously described with reference to FIG. 2. In thisparticular example, an alcohol component of the fuel vapor can beseparated from the hydrocarbon component by way of a fuel separationmembrane 910. Membrane 910 may include any suitable selectivelypermeable membrane that enables an alcohol component of the fuel to passthrough the membrane at a different rate (e.g. a higher rate) than ahydrocarbon component. As one non-limiting example, membrane 910 mayinclude NAFION or other suitable material. Membrane 910 segregates afirst region of separator 920 from a second region 930. Due to theselectivity of membrane 910, the alcohol component of the fuel vapor, asreceived at region 920 via passage 272, can pass through membrane 910and into region 930 at a higher rate than the hydrocarbon component. Insome examples, the membrane may entirely exclude the hydrocarboncomponent from region 930. At least the alcohol component that passesthrough the membrane can be provided to condenser 250 via passage 277,while at least the hydrocarbon component of the fuel vapors can beprovided to the intake manifold of the engine via passage 280. Note thatfuel vapors can be received at vapor separator 240 from evaporator 230via passage 272 or from fuel tank 210 by way of passage 212 fluidlycoupled with passage 272.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The specific routines described herein may represent one or more of anynumber of processing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various acts,operations, or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedacts or functions may be repeatedly performed depending on theparticular strategy being used. Further, the described acts maygraphically represent code to be programmed into the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and nonobvious combinationsand subcombinations of the various systems and configurations, and otherfeatures, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “an” element or “a first” element or the equivalent thereof. Suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Other combinations and subcombinations of the disclosed features,functions, elements, and/or properties may be claimed through amendmentof the present claims or through presentation of new claims in this or arelated application. Such claims, whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

The invention claimed is:
 1. A method of operating a fuel deliverysystem for a fuel burning engine of a vehicle, the method comprising:separating a first fuel and a second fuel from a fuel vapor on-board thevehicle, said fuel vapor including at least an alcohol component and ahydrocarbon component and said first fuel including a higherconcentration of the alcohol component than the fuel vapor and thesecond fuel; condensing the separated first fuel from a vapor phase to aliquid phase; delivering the condensed liquid phase of the first fuel tothe engine; and combusting at least the condensed liquid phase of thefirst fuel at the engine.
 2. The method of claim 1, further comprising,generating said fuel vapor on-board the vehicle from a liquid fuelmixture.
 3. The method of claim 2, wherein the liquid fuel mixtureincludes at least ethanol and gasoline.
 4. The method of claim 3,further comprising, applying heat from a heat source on-board thevehicle to the liquid fuel mixture to generate said fuel vapor beforesaid separating is performed.
 5. The method of claim 4, furthercomprising, applying at least a partial vacuum to a vapor formationregion of the liquid fuel mixture to generate the fuel vapor before saidseparating.
 6. The method of claim 4, wherein said liquid fuel mixtureincludes a higher volatility fraction and lower volatility fraction; andwherein said fuel vapor includes the higher volatility fraction of theliquid fuel mixture; and wherein said method further comprises retainingthe lower volatility fraction of the liquid fuel mixture in a liquidphase during said application of heat.
 7. The method of claim 1, furthercomprising, delivering the lower volatility fraction of the liquid fuelmixture to the engine and further combusting the lower volatilityfraction of the liquid fuel mixture at the engine, said lower volatilityfraction having a lower concentration of the alcohol component than thefirst fuel.
 8. The method of claim 7, wherein the first fuel isdelivered to a cylinder of the engine via a first injector and whereinthe lower volatility fraction of the liquid fuel mixture is delivered tothe cylinder of the engine via a second injector; and wherein the methodfurther comprises, varying an amount of the first fuel delivered to thecylinder relative to an amount of the lower volatility fraction inresponse to an operating condition of the engine.
 9. The method of claim8, wherein the operating condition includes at least one of an engineload and an engine speed.
 10. The method of claim 8, further comprising,operating a compression device fluidly coupled with an air intakepassage of the engine to increase a boost pressure of air received bythe cylinder; and wherein the operating condition includes the boostpressure.
 11. The method of claim 1, wherein said separating the fuelvapor includes passing the fuel vapor through an adsorption canister andadsorbing at least a portion of the hydrocarbon component contained inthe fuel vapor onto a adsorption solid disposed within the adsorptioncanister while passing at least a portion of the alcohol component to acondenser where said condensing is performed.
 12. The method of claim 1,wherein said separating the fuel vapor includes passing at least thealcohol component contained in the fuel vapor through a selectivelypermeable membrane that transports the hydrocarbon component at a lowerrate than the alcohol component.
 13. The method of claim 1, furthercomprising, delivering a vapor phase of the second fuel to an air intakepassage of the engine after said separating; and further combusting thesecond fuel at the engine.